Abstract
An LED curing apparatus cooling system comprising at least one LED mount for mounting a plurality of LEDs; at least one bore in the LED mount; at least one thermal transfer member comprising an evaporator section and a condenser section, wherein the or each thermal transfer member is removably connected to a bore; and wherein each thermal transfer member comprises a collar having an outer surface to mate with an inner surface of a bore.
Claims
1. An LED curing apparatus cooling system comprising at least one LED mount for mounting a plurality of LEDs; at least one bore in the LED mount; at least one thermal transfer member wherein the or each thermal transfer member is removably connected to a bore; and wherein each thermal transfer member comprises a collar having an outer surface to mate with an inner surface of a bore.
2. The LED curing apparatus cooling system according to claim 1, wherein the thermal transfer member is a heat pipe and the collar is attached to the evaporator section of the heat pipe.
3. The LED curing apparatus cooling system according to claim 1, wherein the thermal transfer member is a metal rod and the collar is attached to a first end of the metal rod.
4. The LED curing apparatus cooling system according to claim 1, wherein the outer surface of the or each collar is shaped to mate with a shaped inner surface of a respective bore.
5. The LED curing apparatus cooling system according to claim 1, wherein the outer surface of the or each collar comprises a threaded portion to mate with a threaded inner surface of a respective bore.
6. The LED curing apparatus cooling system according to claim 1, wherein the or each collar is a connecting band.
7. The LED curing apparatus cooling system according to claim 1, wherein the or each collar is an annular band.
8. The LED curing apparatus cooling system according to claim 1, wherein the or each collar is cylindrical having a base at a first end and an opening at an opposing second end.
9. The LED curing apparatus cooling system according to claim 1, wherein the or each thermal transfer member is soldered to a collar.
10. The LED curing apparatus cooling system according to claim 1, wherein the or each LED mount comprises a thermal transfer material between the or each thermal transfer member and the bore.
11. The LED curing apparatus cooling system according to claim 1, wherein the or each LED mount comprises a thermal transfer material between the or each thermal transfer member and the bore and the thermal transfer material has a thermal conductivity greater than about 5 W/mK.
12. The LED curing apparatus cooling system according to claim 1, wherein the or each LED mount comprises a thermal transfer material between the or each thermal transfer member and the bore and the thermal transfer material is a ceramic paste.
13. The LED curing apparatus cooling system according to claim 1, wherein the or each LED mount comprises a thermal transfer material provided between the collar and the bore to which the collar is removably connected.
14. The LED curing apparatus cooling system according to claim 1, comprising one or more LEDs mounted on the LED mount.
15. The LED curing apparatus cooling system according to claim 1, wherein the or each collar comprises copper.
16. The LED curing apparatus cooling system according to claim 1, wherein the or each collar comprises a threaded portion and a non-threaded portion.
17. The LED curing apparatus cooling system according to claim 1, wherein the or each bore is substantially cylindrical.
18. A cooling module for an LED curing apparatus comprising the LED curing apparatus cooling system according to claim 1, wherein the or each thermal transfer member is also connected to at least one air-cooled finned heat sink.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0175] The invention will now be described by way of example with reference to the accompanying drawings, in which:
[0176] FIG. 1 is a cross-sectional view through a cooling system for an LED print curing apparatus in accordance with the present invention.
[0177] FIG. 2a is a perspective view of the thermal transfer member and collar shown in FIG. 1.
[0178] FIG. 2b is a perspective view of an alternative embodiment of the thermal transfer member and collar of the present invention.
[0179] FIG. 3 is a cross-sectional view of the heat pipe and collar shown in FIG. 2a.
[0180] FIG. 4a shows a perspective view of a cooling module for an LED curing apparatus.
[0181] FIG. 4b shows a perspective view of a further embodiment of the cooling module for an LED curing apparatus.
[0182] FIG. 5 shows a side view of a cooling module for an LED curing apparatus as shown in FIG. 4a.
[0183] FIG. 6 shows a view from above of a finned heat sink.
[0184] FIG. 7a shows a view from above of a first finned heat sink interlocking with a second finned heat sink (heat pipes not shown) in a maintenance or assembly configuration.
[0185] FIG. 7b shows a view from above of a first finned heat sink locked to a second finned heat sink (heat pipes not shown) in a use configuration.
[0186] FIG. 8 shows a view from above of a first finned heat sink locked to a second finned heat sink (heat pipes not shown) in a use configuration in an alternative to the present invention.
[0187] FIG. 9 shows a cross section through an LED curing apparatus and the air flow path therethrough for a preferred embodiment wherein air is pulled through the LED curing apparatus.
[0188] FIG. 10 shows a perspective external view of the LED curing apparatus of the FIG. 9 showing the direction of air flow through the apparatus.
[0189] FIG. 11 shows a cross section through an LED curing apparatus and the air flow path therethrough for an embodiment wherein air is blown through the LED curing apparatus.
[0190] FIG. 12 shows a perspective external view of the LED curing apparatus of FIG. 11 showing the direction of air flow through the apparatus.
DETAILED DESCRIPTION
[0191] Referring to FIGS. 1 and 3, the present invention relates to a cooling system 1 for an LED print curing apparatus. The cooling system 1 comprises an LED mount 3. In use a plurality of LEDs 5 are mounted on the LED mount 3. In use, the LEDs are arranged to emit radiation from an outer, substrate-facing side. The cooling system 1 supports a plurality of thermal transfer members, such as a metal rods or copper heat pipes 9, wherein the heat pipes 9 or metal rods sit within the body of the LED mount 3 and transfer heat away from the LEDs 5 to a cooling module 13.
[0192] The cooling system 1 comprises an aluminium LED mount 3, which carries heat generated by the LEDs 5 away from the LEDs 5 to the thermal transfer members, shown in FIG. 1 as copper heat pipes 9. The dimensions of the aluminium heat sink 3 are carefully configured to be fitted within the lamphead of a curing apparatus (not shown). The cooling system 1 comprising the LED mount 3, LEDs 5 and heat pipes 9 form a modular system. In use, multiple cooling systems 1 are arranged along the length of a curing apparatus. The plurality of heat pipes 9 are a passive heat transfer system to efficiently carry heat away from the LEDs 5. In one embodiment of the present invention, the modular system comprises two heat pipes 9 per length of LED mount 3. It is understood that in further embodiments, an alternative thermal transfer member rather than the heat pipe shown in FIGS. 1 and 3 is used; for example, a metal rod.
[0193] With reference to FIG. 1 and FIG. 2a and FIG. 2b, each of the thermal transfer members/copper heat pipes 9, 9′ are provided with a copper collar 7, 7′ which is soldered to the thermal transfer members, such as the copper heat pipes 9 shown in FIG. 2a or the metal rod shown in FIG. 2b. The collar 7, 7′ includes a screw thread 7b, 7b′ on a substantial portion of an outer surface thereof and a smooth, non-threaded portion 7a. The LED mount 3 comprises a series of substantially cylindrical bores 11, which have a threaded inner surface for engagement with the corresponding screw thread 7b, 7b′ on the outer surface of a copper collar 7, 7′. This allows the heat pipes 9 or thermal transfer members, such as metal rods 9′ to be screwed into the bores 11 in the LED mount 3 for secure attachment thereto Referring to FIG. 2a, the collar surrounding the evaporator section of the heat pipe so that each heat pipe 9 is fully contained within the LED mount 3 when fitted to the cooling system 1 . In use, this allows the LEDs 5 to be mounted to the LED mount 3 before the heat pipes 9 are each fitted into a respective bore 11. The collar shown in FIG. 2b is surrounding a first end of the metal rod/thermal transfer member 9′ so that when attached each metal rod/thermal transfer member 9′ is fully contained within the LED mount 33 when fitted to the cooling system 1 In use, this allows the LEDs 5 to be mounted to the LED mount 3 before the thermal transfer members/metal rods/heat pipes 39′, 39 are each fitted into a respective bore 41.
[0194] Referring to FIG. 2b, the collar 7′ and metal rod 9′ are formed as a single piece. This improves thermal transfer and reduces the time and complexity of installation.
[0195] The present invention, shown in FIGS. 1, 2a, 2b and 3 significantly improves the ease of installation of the thermal transfer members/heat pipes 9′, 9 within a curing apparatus. In use, the LEDs 5 are attached to the LED mount 3 and the thermal transfer members/heat pipes 9′, 9 are attached at a later stage. This minimises the installation time in a clean room because only the LEDs need to be installed in this controlled environment, whilst other components of the cooling system can be installed at the location of use of the apparatus. Multiple LED mounts 3 having LEDs 5 attached thereto are installed in the chassis of a curing apparatus before the thermal transfer members/heat pipes 9′, 9 are screwed into the LED mount 3 and attached thereto by the mating engagement of the screw thread 7b on the outer surface of the collar 7 with the threaded inner surface of the bore 11 into which the thermal transfer members/heat pipe 9′, 9 is received. The present invention allows for ease of assembly of the LED mounts 3 into the curing apparatus before the thermal transfer members/heat pipes 9′, 9 and further cooling components are installed. Furthermore, the thermal transfer members/heat pipes 9′, 9 and other cooling components can be removed and replaced; for example, if these components fail or require cleaning, without the sealed chassis of the apparatus containing the LEDS being removed. Removal of the LEDS is more likely to damage the delicate LEDs. The present invention significantly reduces the risk of damage or contamination of the LEDs.
[0196] A ceramic paste (not shown) is provided between the outer surface of each of the heat pipe collars 7′, 7 and the respective inner surface of the bore 11 in which the thermal transfer members/heat pipe 9′, 9 is held. The ceramic paste prevents voids forming between the collar 7′, 7 and the bore 11, which ensures optimum thermal contact between the LED mount 3 and the thermal transfer members/heat pipes 9′, 9 because there are no thermal barriers to the heat transfer away from the LED mount 3 and so away from the LEDs 5, in use.
[0197] In the example shown in which corresponding screw threads 7b, 7b′ are provided on the external surface of the collar 7, 7′ and the internal surface of the bore 11, it will be appreciated that the ceramic paste can be applied to one or both threaded surfaces before the thermal transfer members/heat pipes 9′, 9 are screwed into the LED mount 3. During installation, the rotation of the external threaded surface of the collar 7, 7′ against the internal threaded surface of the bore 11 spreads the ceramic paste so that any voids are eliminated.
[0198] Referring to FIGS. 1 and 2a, in use, the central core of each heat pipe 9 contains a liquid, such as water or ammonia, which prior to heating is held by a wick structure (not shown). The heat pipe 9 contains a vacuum so that the liquid will boil and take up heat generated by the LEDs 5 at a temperature below the boiling point of the liquid at atmospheric pressure. The water will boil and effectively transfer latent heat from the LEDs 5 modules at this lower temperature. In use, when the LED print curing apparatus is switched on and the LEDs 5 are radiating to cure a substrate, heat generated by the LEDs 5 is transferred away from the rear, inner face of the LEDs 5 to the LED mount 3. Heat is carried away from the LED mount 3 by the heat pipe/s 9 to a cooling module 13. On heating, the liquid held within the core of the heat pipe 9 is vaporised and the heat is carried away before the liquid re-condenses and the wick transports the liquid back to the base of the heat pipe 9. The heat pipe/s 9 ensures that heat is carried away quickly and efficiently from the LEDs 5 and condensation of the liquid contained within the core of the heat pipe 9 is enhanced by capillary action.
[0199] As shown with particular reference to FIGS. 2a, 2b and FIG. 3, in order to increase the contact surface area of the collars 7, 7′ and the bores 11, the outer walls of the collars are shaped to fit against correspondingly shaped walls of the bores 11. Each collar 7, 7′ has a smooth, rounded base section 7a, 7a′ which is received into a bore 11. The mechanical fit of the threaded portion 7b, 7b′ with the threaded portion of the bore 11 in addition to the heat transfer material (not shown) between the external surface of the collar 7/heat pipe 9 shown in FIG. 2a or the collar 7′/metal rod 9′ and the internal surface of the bore 11 ensures that there are no voids such that thermal transfer is optimised.
[0200] As shown in FIG. 1, the evaporator section of each thermal transfer member/heat pipe 9 is adjacent to the LED mount 3 and the LEDs 5 that are mounted thereon. The opposing end - i.e., the condenser end of each heat pipe 9 is held within a cooling module 13. In a preferred embodiment, the cooling module 13 is an air-cooled finned heat sink.
[0201] Referring to FIGS. 4a and 4b, FIG. 5 and FIG. 6, a cooling module 31 is shown and comprises a first finned heat sink 33, 33′ and a second finned heat sink 35, 35′. The first finned heat sink 33, 33′ is substantially symmetrical to the second finned heat sink 35, 35′ about a central axis 37 or midline where the internal surface 33a of the first heat finned sink 33 is proximal to and spaced apart from the internal surface of the second heat finned sink 35. Each finned heat sink 33, 35 is an aluminium extrusion and is shaped to maximise heat transfer away from the heat sink 33, 35 through a plurality of fins 39, which are substantially cuboidal, and each fin protrudes perpendicular to the central axis 37. The plurality of fins 39 are equally spaced from each other so that each fin 39 is spaced from the adjacent fin 39 by a uniform distance. For example, each fin 39 has a width of about between about 1.5 mm and 5 mm and is spaced from the adjacent fin 39. In a preferred embodiment, the fin 39 has a width of about 1.5 mm at its tip with a width increasing towards the midline of the fin with a pitch of 3.5 mm.
[0202] Referring to FIGS. 4, 4b and 7, the internal surface 33a of the first finned heat sink 33 comprises a series of semi-cylindrical recesses 33b. The internal surface (not shown) of the second finned heat sink 35 also comprises a series of semi-cylindrical recesses 35b and is symmetrical about the central axis 37 where the internal surface 33a of the first finned heat sink 33 is proximal to the internal surface 35a of the second finned heat sink 35. That is, each of the recesses 33b, 35b have the shape of a longitudinal half of a cylinder. As shown in FIGS. 4a and 4b, when the first finned heat sink 33 is removably secured to the second finned heat sink 35 the internal face of the first heat sink 33a is spaced apart from the internal face of the second heat sink 35a so that a plurality of substantially cylindrical recesses 41 are formed therebetween.
[0203] Referring to FIG. 4a, FIG. 4b, and FIG. 5, in a use configuration, the cooling module 31 is secured to a plurality of thermal transfer members, shown as heat pipes 50. In alternative embodiments, the cooling module is secured to a plurality of thermal transfer members; for example, a metal rod or a metal pipes, such as a copper rod or a copper pipe. A heat pipe 50 is received in each of the cylindrical recesses 41. Each heat pipe 50 is held securely within the cooling module 31 to ensure optimum thermal contact between the condenser section of the heat pipe 50 and the cylindrical recess 41 into which the heat pipe is received. The heat pipes 50 secure the first and second finned heat sinks 33, 35 of the cooling module 31 in a tight clamping arrangement. The semi-cylindrical recesses 33b, 35b are substantially the same radius as the outer radius of the heat pipe 50. For example, each heat pipe has a radius of about 4 mm and the cylindrical aperture formed by the semi-cylindrical recesses 33b, 35b have a radius of about 4 mm. This ensures that each heat pipe 50 is firmly held in place and that the heat transfer is as efficient as possible from each heat pipe 50 to the surrounding finned heat sink 33, 35. This maximises the heat transfer away from each heat pipe 50 to the fins 39 of each heat sink 33, 35.
[0204] Referring to FIGS. 6, 7a and 7b, each finned heat sink 33, 35 comprises an interlocking tab 45. In the embodiment shown in FIG. 6, the interlocking tab 45 is substantially L-shaped.
[0205] Referring to FIG. 7a, in a maintenance configuration, each of the plurality of thermal transfer members, such as heat pipes or metal rods (not shown) are located and held within a cylindrical recesses 41 between the first finned heat sink 33 and the second finned heat sink 35. The tab 45 of the first finned heat sink 33 interlocks with the tab 45 of the second heat sink 35 so that the cooling module 31 is held around the thermal transfer members/heat pipes but can be adjusted to allow for ease of insertion of multiple thermal transfer members/heat pipes into the cooling module. The interlocking tabs 45 stay linked whilst allowing partial movement of the first finned heat sink 33 and the second finned heat sink 35 around the thermal transfer members/heat pipes. In this maintenance configuration there is a small gap between the tab 45 of the first finned heat sink 33 that is interlocked to abut with the tab 45 of the second heat sink 35.
[0206] For installation of the cooling module, the thermal transfer members/heat pipes/metal rods 50 are first fitted to an LED heat sink on which LEDs are mounted. A carefully measured dose of heat transfer paste is applied to the semi-cylindrical recesses 33b, 35b of both the first finned heat sink 33 and the second finned heat sink 35. The first finned heat sink 33 and the second finned heat sink 35 are then interlocked as far as the interlocking tabs 45 allow. The interlocked finned heat sinks 33, 35 are then precisely lowered over and around the heat pipes 50. The first finned heat sink 33 is spaced apart from the second finned heat sink 35 when they are brought together to form the cylindrical apertures. The first finned heat sink 33 and the second finned heat sink 35 are mechanically clamped together by the interlocking tabs 45 for ease of installation.
[0207] Referring to FIG. 7b, when all of the required thermal transfer members/heat pipes (not shown) are held in the desired position a locking pin 47 is inserted into the or each small gap between the tab 45 of the first finned heat sink 33 that is interlocked with the tab 45 of the second heat sink 35. In this final stage of installation, insertion of the locking pin 47 releases the mechanical clamp between the interlocking tabs 45 to transfer the locking force to the or each locking pin 47. The locking pin 47 is a tension pin or a spring pin. Referring to FIG. 4b, in an alternative embodiment a screw 17′, for example, a threaded screw, is inserted into the or each small gap between the tab (not shown) of the first finned heat sink 3 that is interlocked with the tab (not shown) of the second finned heat sink 5.
[0208] Referring to FIGS. 7b and 6, insertion of a locking pin 47 in a direction parallel to the axis of the cylindrical recess 41 forces the tab 45 of the first finned heat sink 33 into locking engagement with the tab 45 of the second finned heat sink 35. Thus, each thermal transfer member, shown as heat pipe 50 is held securely with the cylindrical recess 41 in the cooling module 31 so that the condenser section is held against the finned heat sinks 33, 35 for optimum thermal transfer of heat from the heat pipe 50 to the fins 39.
[0209] Referring to FIG. 5, the evaporator section of each of the heat pipes 50 protrudes from the base of the cooling module 31 to be secured proximal to the LED heat sink in the lamphead.
[0210] Referring to FIGS. 7a and 7b, in a maintenance position without the locking pin or screw inserted, the first and second finned heat sinks 33, 35 can move in a direction shown by arrow A towards and away from a heat pipe/s contained between them in the cylindrical recesses. Referring to FIG. 7b, when the locking pin 47, or in alternative embodiments a screw, is inserted, in a use position, the first and second finned heat sinks 33, 35 are forced towards each other in a direction shown by arrow B so that their internal surfaces are proximal to each other and are locked in position.
[0211] In use with an LED curing apparatus, a plurality of cooling modules are arranged along the length of the LED curing apparatus around a plurality of thermal transfer members, for example heat pipes or metal rods. The cooling modules have a length of about 25 mm and are arranged substantially along the full length of the lamphead and are locked in place by the locking pins. For known devices, the thermal transfer members, for example heat pipes or metal rods are spaced at increments of about 2.5 cm for a range of lengths from 2.5 cm to 250 cm. The cooling modules are configured so that the cooling modules can be conveniently installed on site; for example, during an on-site repair. The cooling modules can be fixed to the thermal transfer members, for example heat pipes or metal rods, after the LEDs are attached to the LED heat sink.
[0212] The lamphead comprises an array of LED modules (not shown), wherein each LED module is a unit containing one or more LEDs. In use, each LED is a radiation source for curing print or a coating on a substrate (not shown). It is understood that the LED modules form a linear radiation source to direct radiation continually onto a substrate during curing. The LED modules comprise boards that rest on a heat sink (not shown). This LED heat sink is adjacent to the evaporator section of each of the plurality of heat pipes.
[0213] In use, the LEDs are arranged to emit radiation from an outer, substrate-facing side through a “curing window” onto a substrate (not shown) to be cured. In alternative embodiments, the “curing window” comprises a lens or reflector. The lamphead is an elongate shape and can be fitted directly onto a machine, or is a slideable cuboidal cassette which, in use, is slideable into a housing. When inserted into the housing, the LED modules form a solid radiation emitting face.
[0214] Referring to FIGS. 4a and 5 in use, heat is transferred away from the inner face of the LED modules to the evaporator section of the heat pipes 50. Heat is carried from the evaporator section of each heat pipe 50 to the condenser section that is held substantially within the cooling module 31. Heat is then efficiently transferred though the first and second finned heat sink 33, 35 so that the LEDs are rapidly and efficiently cooled. Furthermore, the configuration of the present invention ensures that the cooling modules 31 hold the heat pipes 50 in place, achieving good thermal contact between the finned heat sinks 33, 35 and the heat pipes 50, wherein the clamping force between the heat sinks 33, 35 and the heat pipes 50 is uniform along the length of the cooling module 31.
[0215] The heat pipes 50 of the present invention use known heat pipe technology to take up heat generated by the LED modules (not shown). In use, when the lamphead is switched on and the LEDs are radiating to cure a substrate, heat generated by the LEDs is transferred away from the rear, inner face of each LED module to an aluminium heat sink (not shown). Heat is carried away from the LEDs and the copper heat sink by the heat pipe/s 50 and is then carried away from the heat pipes 50 by the first and second finned heat sinks 33, 35. On heating, the liquid held within the core of the heat pipe 50 is vaporised and the heat is carried away before the liquid re-condenses and a wick transports the liquid back to the base of the heat pipe 50. Heat is rapidly transferred from the LED modules to the heat pipes 50 and to the cooling modules.
[0216] Referring to FIG. 4a and FIG. 4b, to access the thermal transfer members 50, 50′ for maintenance or repair, the pins 47 or screws 47′ securing the cooling module 31 around the heat pipes 50 are removed. With the pins 47 removed, the first finned heat sink 33 is able to move away from the second finned heat sink 35 increasing the size of the cylindrical recesses and allowing the cooling module 31 to be removed from the heat pipes 50. Movement of the first finned heat sink 33 and second finned heat sink 35 away from each other causes the locking tabs 43, 45 to move into an interlocking position. This maintains the first finned heat sink 33 interlocked with the second finned heat sink 35 so that the components of the cooling module 31 remain assembled when the cooling module is in a maintenance configuration. The cooling module 31 can then be removed from the thermal transfer members; i.e. the heat pipes 50 shown in FIG. 4a and the metal rods shown in FIG. 4b, if required.
[0217] Referring to FIGS. 9 and 10, an LED curing apparatus 51 is shown comprising a housing 53. The housing 53 comprises an outer casing wherein LEDs (not shown) are mounted at the base 58 of the housing 53 and an air inlet 77 is positioned in an upper face 59 of the housing 53. The air inlet 77 is an elongate opening along substantially the entire length of the upper face of the apparatus 51. The base 58 of the LED curing apparatus 51 is the substrate-facing surface with the or each LED radiation source arranged thereon. In a preferred embodiment, the LED radiation source is a UV radiation source. In alternative embodiments, the LED radiation source is an infra-red radiation source. The upper face of the apparatus 51 is substantially parallel to and spaced apart from the base of the apparatus 51. An air outlet 52 is positioned at a first end 56 of the apparatus 51, wherein the first end 56 is perpendicular to and between the base 58 and the upper face 59 of the apparatus 51. The air outlet 52 is attached to ducting connected to a source of ambient or cooled air.
[0218] The LED curing apparatus 51 comprises a plurality of LEDs (not shown) mounted to an LED mount. The inner walls of the housing 53 and the cavities formed therein are shaped to control air pressure and air flow through the LED curing apparatus 51. The housing 53 is substantially cuboidal comprising outer walls 53 and inner walls 70 to which further components are mounted. The shape of the inner walls of the housing 53 controls air pressure and so air flow through the device.
[0219] Referring to FIG. 9, an inner wall of the housing 70 defines an upper air channel 72 through which air from the air inlet 77 passes into the curing apparatus 51. The upper air channel 72 is parallel to the outer walls 53 of the housing. Preferably, the width of the upper air channel 72 is about 4 mm. The upper air channel 72 increases in width to about 10 mm and passes from the air inlet 77 to an inlet cavity or void 71.
[0220] A plurality of thermal transfer members, shown in FIGS. 9 and 10 to be heat pipes 14, are mounted along the length of the LED curing apparatus 1. In alternative embodiments, an alternative thermal transfer member is used; for example, as shown in FIG. 1b, the thermal transfer member is a metal rod. In the embodiment shown in FIG. 9, each heat pipe 64 is held securely within a cooling module 57, ensuring optimum thermal contact between the heat pipe 64 and a substantially cylindrical recess into which each heat pipe is received. The or each thermal transfer member/ heat pipe 64 passes through the inlet cavity or void 71 of the housing 53. The cooling module 57 comprises a first finned heat sink 61 and a second finned heat sink 63. The first finned heat sink 61 is substantially symmetrical to the second finned heat sink 63 about a central axis or midline. Each finned heat sink 61, 63 is shaped to maximise heat transfer away from the heat sink 61, 63 through a plurality of fins (not shown), which are substantially cuboidal. In alternative embodiments, it is understood that equivalent heat sinks could be used. For example, an arrangement of pins or blades could be used, including a skived heat sink. It is also envisaged that alternative configurations of the present invention include finned heat sinks in alternative positions to carry heat away from the thermal transfer members, which are either heat pipes or metal rods.
[0221] The inner walls of the housing 53 define a main cavity or void 71 below the or each finned heat sink 61, 63 and a second cavity or outlet void 74 above the or each finned heat sink 61, 63 through which heated air 75 exits the LED curing apparatus 51. For example, the cross-sectional area of the air path through the outlet void 74 is about 1.2 times greater than the cross-sectional area of the air path through the inlet void 71.
[0222] The first finned heat sink 61 and the second finned heat sink 63 are removably held within the housing 53 by a shaped extrusion 65 comprising a base 67a, 67b and two upstanding walls 68. The base 67a, 67b and upstanding walls 68 are formed of a shaped extrusion, wherein each upstanding wall 68 is substantially perpendicular to the base 67a, 67b and held within the outer walls of the housing 53. The base 67 comprises a first base member 67a and a second base member 67b, which are substantially parallel to the LED mount. The first and second base members 67a, 67b partially cover the base of the respective finned heat sink 61, 63. The first finned heat sink 61 is housed above the first base member 67a and the second finned heat sink 63 is housed above the second base member 67b. The base members 67a, 67b are spaced apart from each other to form a restriction in the air flow through a gap therebetween to provide an air inlet 69 into the finned heat sinks 61, 63 through which air is pulled.
[0223] Referring to FIGS. 9 and 10, air is pulled into the apparatus by a source of air connected by ducting to the outlet 52. Typically, the air pressure at the outlet ducting is about -2050 Pa relative to ambient pressure and the pressure of air drawn into the air inlet 77 is between about -350 Pa to -500 Pa relative to ambient pressure. The air pressure is higher at the inlet 77 to the apparatus to create suction so that air is pulled through the apparatus 1 from the inlet 77 to the outlet 52. The air 76 flows from the inlet 77 around an air passage 72 along the inner walls of the housing 53 and enters the open, inlet cavity/void 71 below the or each finned heat sink 61, 63 to expand such that air pressure decreases to about -500 Pa to -450 Pa relative to ambient pressure. The air from the open cavity/void 71 adjacent to the LED mount then flows, i.e., is pulled into the finned heat sinks 61, 63 to carry heat away from the heat sinks 61, 63.
[0224] The air inlet 69 into the finned heat sinks 61, 63 controls i.e., throttles the air flow entering the finned heat sinks 61, 63 from the inlet cavity 71 of the housing 53 to create a turbulent flow of air through the finned heat sinks 61, 63. When the heated air 75 is carried out of the finned heat sinks 61, 63 it expands into the second cavity or outlet void 74 so that pressure decreases again.
[0225] The restriction 67a, 67b proximal to the or each finned heat sink 61, 63 reduces the cross sectional area of the air flow path from the open inlet cavity 71 below the finned heat sink 61, 63. The reduction in the cross sectional area of the air flow path from the inlet cavity 71 to the finned heat sinks 61, 63 is by a ratio of about 1:2.3 (inlet cavity:finned heat sink). The reduction in the cross-sectional area of the air flow path from the cavity 71 below the heat sinks 61, 63 to the or each finned heat sink 61, 63 reduces by more than 50%. In an example apparatus 51, the air inlet 69 between the outer wall of the thermal transfer member/ heat pipe 64 and the restriction 67a, 67b is about 8.5 mm (A) so that the open area per heat sink is about 410 mm.sup.2. Air enters the finned heat sinks 61, 63 through the air inlet 69 and passes across the fins of the heat sinks 61, 63, wherein the distance (B) along, i.e., the length of each fin from the outer wall of the thermal transfer member/heat pipe 64, is about 19.5 mm. When air flows into the heat sinks 61, 63, the restriction of the air flow by the first and second base members 67a, 67b causes significant turbulence of the air passing into the finned heatsinks 61, 63, which increases heat transfer from the fins to the surrounding air. This increases the cooling achieved by the finned heat sinks 61, 63.
[0226] The size and shape of the housing 53, the air inlet 77, the air passage 72, the cavity 71, the base supports 67a, 67b and the second cavity/outlet void 74 are carefully configured to decrease relative air pressure moving through the apparatus 1 and maximise cooling of the finned heat sinks 61, 63. The configuration of the present invention ensures that air flows through the apparatus 51 to carry heat away from the thermal transfer members 64, for example heat pipes 64 or metal rods (not shown) and ensures that cooling is substantially uniform along the length of the device 51. The air in the inlet cavity 71 below the finned heat sinks 61, 63 is at a higher pressure than the air in the outlet cavity 74 above the finned heat sinks 61, 63. The air pressure decreases when the air moves out of the finned heat sinks 61, 63 to the outlet cavity 74.
[0227] The air pressure outside the apparatus 51 at the air inlet 77 through which air is pulled into the apparatus 51 is about +101 kPa. The air pressure decreases when the air reaches the open sections/cavities 71, 74 into which it expands. The air pressure in the inlet cavity 71 is about -600 Pa relative to ambient pressure and the air pressure of the heated air 75 exiting the finned heat sinks 61, 63 that is pulled towards the air outlet 52 is about -1150 Pa relative to ambient pressure.
[0228] The present invention can be configured for any length of apparatus - i.e., according to the required application. The ratios of the air path sections as air flows from the air inlet 77 to the air outlet 52 is controlled to achieve the required air flow and so uniform cooling along the length of the apparatus 51.
[0229] Examples of the cross-sectional areas of the air flow passage though each section of the apparatus 51 are set out in Table 1 below for an apparatus having a 30 cm length:
TABLE-US-00001 Position 30 cm length apparatus cross sectional area of the air flow passage (mm.sup.2) Air inlet (27) 1964 Air inlet into the finned heat sinks (19) 3280 Outlet cavity (24) 3910 Outlet ducting 6718
[0230] Referring to FIG. 10, in a preferred embodiment of the present invention, air 73 is pulled into the air inlet 77, which is along the length of the housing 53, from a single fan (not shown) at the air outlet 552 at a first end 6 at the rear of the housing 553. The fan can be connected to the housing 53 by ducting and the fan is positioned remotely from the apparatus 51. Referring to FIG. 9, air 76 is pulled through the housing 53 and enters the cooling module 57 through the air inlet 69 between the first base member 67a and the second base member 67b. The air inlet 69 effectively controls the air flow entering the cooling module 57. The air inlet/gap 69 through which air enters the finned heat sinks 61, 63 chokes - i.e., restricts and controls the air flow into the finned heat sinks 61, 63. The air then passes along the plurality of fins and through the first and second finned heat sinks 61, 63 adjacent to the thermal transfer members 64, for example, heat pipes 64 or metal rods. The heated air 75 is pulled out of the housing 53 to the outlet cavity 74 and to the outlet 52 to exit and so cool the LED curing apparatus 51.
[0231] With reference to FIG. 9, the uniformity of pressure, air flow and so cooling along the length of the apparatus 51 was measured by positioning sensors at fixed points (Position 1 - air inlet channel 72; Position 2 - air channel into open cavity 71 ; Position 3 - outlet cavity 74). It can be seen from the results shown in Table 2 below that the pressure measurements are substantially uniform along the length of the apparatus:
TABLE-US-00002 Gauge pressure (Pa) — relative to ambient pressure Measurement Point Position along the length of the apparatus (mm) 116.25 192.75 269.25 345.75 1 –357 –377 –473 –440 2 –650 –783 –757 –823 3 –483 –470 –473 –447
[0232] Referring to FIGS. 11 and 12, an LED curing apparatus 51′ of an alternative embodiment is shown, cool air 73′ is blown into and along the length of the housing 53′ from a single fan (not shown) into the air inlet 52″ at a first end (rear) of the housing 53′. The fan can be connected to the housing by ducting and the fan is positioned remotely from the apparatus 51′. The cool air 73′ enters the cooling module 57′ through the air inlet 69′ between the first support 67a′ and the second support 67b′. The air inlet 69′ effectively controls the air flow entering the cooling module 57′. The air inlet/gap 69′ through which air enters the finned heat sinks 61′, 63′ chokes -i.e., restricts and controls the air flow into the finned heat sinks 61′, 63′. The air then passes along the plurality of fins and through the first and second finned heat sinks 61′, 63′ adjacent to the condenser section of the heat pipe. The heated air 75′ rises upwards through the cooling module 57′ to the outlet 77′ to leave the housing 53′.
[0233] The above described embodiments have been given by way of example only, and the skilled reader will naturally appreciate that many variations could be made thereto without departing from the scope of the claims.
[0234] Within this specification embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without parting from the invention. For example, it will be appreciated that all preferred features described herein are applicable to all aspects of the invention described herein and vice versa.
[0235] Within this specification, the term “about” means plus or minus 20%, more preferably, plus or minus 10%, even more preferably, plus or minus 5%, most preferably, plus or minus 2%.
[0236] Within this specification, the term “substantially” means a deviation of plus or minus 20%; more preferably, plus or minus 10%; even more preferably, plus or minus 5%, most preferably, plus or minus 2%. Within this specification, reference to “substantially” includes reference to “completely” and/or “exactly.” That is, where the word substantially is included, it will be appreciated that this also includes reference to the particular sentence without the word substantially.
